Tailoring luminescent patterns with rare-earth photonic materials for anti-counterfeiting applications: A lightkey

Anti-counterfeiting strategies are competitively developed against fast-growing counterfeit markets as a cornerstone for the next generation of luminescent security inks, so it will be more difficult to mimic by ever increasing sophisticated counterfeiters. In particular, rare-earth doped up-conversion luminescent materials present important advantages such as invisibility in ambient light, excitation by low cost NIR irradiation, lack in background noise and negligible auto-fluorescence from the surface. Here we present colour tuneable upconversion emissions in two families of rare-earth doped photonic materials (sol-gel derived nano-glassceramics and glasses prepared by melt quenching technique) for tailoring the overall emitted luminescence, as a sort of lightkey. In particular, intensity ratios among UV and VIS up-conversion emission bands can be tuned by modifying doping concentration level and excitation power density, as an additional security feature itself, giving rise to a multi-digit security code based on light-responsive encrypted patterns.

Automated summary

Anti-counterfeiting strategies are developed to combat counterfeit markets and prevent sophisticated counterfeiters from mimicking luminescent security inks. Rare-earth doped up-conversion luminescent materials offer advantages such as invisibility in ambient light, low cost excitation, absence of background noise, and minimal auto-fluorescence. This study focuses on color tuneable upconversion emissions in two types of rare-earth doped photonic materials, allowing for tailored luminescence and creating a light-responsive encrypted security code based on intensity ratios of UV and VIS up-conversion emission bands.